International Immunology, Vol 10, 147-158, Copyright © 1998 by Oxford University Press
A Hasegawa, Y Ueno, M Yamashita, T Nakayama and T Tada
Regulatory mechanisms of T cell autoreactivity to MHC class II molecules
were studied in transgenic (Tg) mice with auto-I-Ak-reactive TCR alphabeta
transgenes (designated as MS Tg mice). Our previous study revealed that the
T cell tolerance established in autoreactive MS Tg mice was not due to
either clonal deletion in the thymus, anergy or an active suppression in
the periphery. We proposed a novel form of self tolerance termed 'clonal
insufficiency', where autoreactive T cells were conditionally rendered
unresponsiveness to self antigen in vivo, although retaining full potential
reactivity in in vitro conditions. Here, we investigated the role of
co-stimulatory molecules for the induction of self tolerance with 'clonal
insufficiency'. MS Tg mice were mated with CD80 (B7-1) Tg mice in which B
cells exclusively and constitutively expressed CD80 molecules. Both MS Tg
mice and CD80 Tg mice by themselves showed no evidence for activation of T
cells and B cells, whereas MS x CD80 double-Tg mice with a H-2k background
revealed an abnormal increase in the number of splenocytes and in the
expression of activation markers (CD69 and CD25) on CD4 T cells in the
spleen. These results indicated that the self tolerance established in MS
Tg mice involved a down-regulation of CD80 molecules on B cells in vivo,
resulting in a failure of sufficient T-B interactions. In addition, the
serum concentration of IL-10, one of the down-regulators of CD80
expression, was found to be increased significantly in MS Tg mice. The
autoreactivity of MS Tg T cells detected in vitro was significantly blocked
by recombinant IL-10. Thus, IL-10-mediated down-regulation of CD80 on B
cells was suggested to be involved in the clonal insufficiency in MS Tg
mice in vivo.
ARTICLES
Regulation of T cell autoreactivity to MHC class II by controlling CD80 (B7-1) expression on B cells
Research Institute for Biological Sciences and Faculty of Pharmaceutical Sciences, Science University of Tokyo, Chiba, Japan.
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